Brake Cooling Fluid Diverter for an Off-Highway Machine

ABSTRACT

The disclosure relates, in one aspect, to a friction brake cooling system for a machine. The cooling system includes at least one pump connected to at least one reservoir containing cooling fluid. A controller is configured to divert a cooling fluid flow through a valve to a first friction brake system and to a second friction brake system based on the use of the systems. In another aspect, the disclosure relates to a method of cooling a first friction brake system and a second friction brake system including diverting a flow of brake cooling fluid to the systems based on the use of the systems.

TECHNICAL FIELD

This patent disclosure relates generally to a brake cooling system and,more particularly, to brake cooling fluid systems and methods to controlbrake cooling fluid systems.

BACKGROUND

Braking systems are used in a large variety of machines and vehicles tocontrol, slow and stop the machine. Exemplary machines include passengervehicles, trains, dump trucks, and mining vehicles. Moreover, machinesincreasingly use electric drive systems to provide propulsion. Forexample, passenger vehicles may use a hybrid drive system whereby atraditional internal combustion engine and an electric motor are used toprovide propulsion for the vehicle. Machines, such as a railway enginesand off-road vehicles may use a diesel powered engine to drive agenerator, which provides electric power to a motor. The motor thenprovides propulsion for the machine.

Braking systems may take advantage of components in electric drivesystems to provide braking for machines. For example, a hybrid passengervehicle may include a regenerative braking system whereby the vehicle isslowed by the electric drive system while at the same time a battery inthe vehicle is recharged and railway engines may use dynamic retardingto slow the train. Although brake systems utilizing electric drivesystems have been used, these systems cannot stop a machine traveling athigh speed quickly, nor can these systems consistently slow a heavilyloaded machine traveling downhill or in slippery conditions.

Some prior systems include a manual retarder lever that enables theoperator to control ground speed by manually selecting the level ofretarding or automatic retarder control that automatically controlsmachine speed based upon the operator's machine speed setting. Themanual or automatic retarder may control an electric retarding system.Additionally, the operator may control a traditional braking pedal toactuate hydraulic brakes. In this way, the operator can manually controlboth dynamic retarding and hydraulic brakes. Nevertheless, thisconfiguration may be difficult for an operator to control effectively.For example, if the speed setting lever is set to high, the operator mayhave to rely more on the service brakes. In a large, heavily loadedmachine, this may lead to the service brakes overheating. In addition,excess service brake wear may occur on a machine if the service brakesare used for continuous retarding.

One exemplary braking system is described in U.S. Pat. No. 6,441,573 toZuber et al. This system describes an electrical and friction brakingsystem. However, the system does not vary the ratio of braking torquesbased upon user controls, nor based upon whether the electric brakingsystem is meeting the requested retarding needs of the machine.

Some prior systems use brake cooling oil to reduce the risk of theservice brakes overheating. Cooling oil may be pumped to the servicebrakes when they are activated and to minimize the likelihood that theservice brakes will overheat. One exemplary brake cooling system isdescribed in U.S. Pat. No. 4,083,469 to Schexnayder and assigned toCaterpillar Inc. The described system includes disc brake assemblies.The assemblies include valves for cooling fluid to communicate with abrake assembly. Cooling flow is automatically activated upon a hightemperature condition in the brakes. While the described system willadvantageously cool the brakes, it does not direct additional coolingoil flow to brake assemblies based on their actual or expected use inthe system.

The foregoing background discussion is intended solely to aid thereader. It is not intended to limit the disclosure, and thus should notbe taken to indicate that any particular element of a prior system isunsuitable for use within the disclosure, nor is it intended to indicatethat any element, including solving the motivating problem, is essentialin implementing the systems and methods described herein. Theimplementations and application of the systems and methods describedherein are defined by the appended claims.

SUMMARY

The disclosure describes, in one aspect, a method of cooling a firstfriction brake system and a second friction brake system in a machinehaving a brake cooling system. The brake cooling system includes a brakecooling fluid and a brake cooling fluid diverter. The method determineswhether the first friction brake system is activated. The methoddetermines whether the second friction brake system is activated. Brakecooling fluid is circulated through the brake cooling system to thefirst friction brake system and to the second friction brake system. Thebrake cooling fluid is diverted to the first friction brake system andthe second friction brake system based on the use of the first frictionbrake system and the second friction brake system.

In another aspect, the disclosure describes friction brake coolingsystem for a machine. At least one pump connects to at least onereservoir containing cooling fluid and is configured to provide acooling fluid flow. At least one valve is in fluid communication withthe pump. A first friction brake system is in fluid communication withthe valve and a second friction brake system is in fluid communicationwith the valve such that cooling fluid from the reservoir is pumpedthrough the valve to the first friction brake system and to the secondfriction brake system. Further, at least one controller is configured todivert the cooling fluid flow through the valve to the first frictionbrake system and to the second friction brake system based on the use ofthe first friction brake system and the use of the second friction brakesystem.

In another aspect, the disclosure describes an off-road work machinehaving an engine powering at least one pump in a first set of pumps andat least one pump in a second set of pumps. The machine further includesa first friction brake system associated with a front set of wheels anda second friction brake system associated with a rear set of wheels. Acooling fluid reservoir contains cooling fluid and is connected to thefirst set of pumps and the second set of pumps. A controller monitorsthe first friction brake system and the second friction brake system.The machine further includes a valve connecting the first set of pumpsand the second set of pumps to the first friction brake system and thesecond friction brake system such that the valve can vary a coolingfluid flow to the first friction brake system and the second frictionbrake system in response to signals received from the controller.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is a schematic view of an electric drive system including anelectric retarding system for a machine.

FIG. 2 is a logical block diagram illustrating a braking system for amachine including hydraulic friction brakes, a brake oil cooling systemand an electric retarder.

FIG. 3 is a flow chart illustrating one embodiment of a braking controlprocess for a machine including hydraulic friction brakes and anelectric retarder.

FIG. 4 is a logical block diagram illustrating one embodiment of a brakecooling flow system for a machine including friction brakes.

FIG. 5 is a flow chart illustrating one embodiment of a brake oilcooling diverter control process for a machine.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates a schematic view of anexemplary electric drive system including an electric retarding systemfor a machine. The exemplary electric drive system includes an engine100. Suitable engines include gasoline powered and diesel poweredinternal combustion engines. When in a drive configuration, the engine100 powers a generator 102. The generator 102 produces three-phasealternating current. The three-phase alternating current passes througha rectifier 104, which converts the alternating current to directcurrent. An inverter or invertors 106 convert the direct current tovariable frequency back to alternating current which feeds a motor 108.By controlling the frequency of the current produced by the invertors106, the speed of the motor 108 is controlled. The motor 108 producestorque which powers the drive wheels 110.

In an alternative embodiment, an engine is not needed and the motor 108is driven directly from an electric power source, such as a battery. Insome embodiments, one motor powers all drive wheels. In alternativeembodiments, various numbers of motors are used to power drive wheels.For example, each drive wheel may have an individual motor associatedwith the wheel.

When operating in an electric braking, also known as electric retarding,configuration, the drive wheels 110 power the motor 108. Driving themotor 108 places a torque on the drive wheels 110 and causes them toslow, thus braking the machine. The motor 108 generates alternatingcurrent. The inverters 106 convert the alternating current to directcurrent and feed the current to a chopper 112, which acts as a directcurrent to direct current convert, and resistor grid 114. The powergenerated by the motors 108 is thus dissipated as heat by the resistorgrid 114. However, in alternative embodiments, the power generated bythe motors 108 may be stored for later use. In one embodiment, the powergenerated by the motors 108 is stored in an electric battery. The energyin the electric battery can then be used in drive mode to power themotors 108 and propel the machine.

As contemplated, the braking system operates in two modes. In a firstmode, the electric retarder supplies as much of the requested brakingtorque as is possible. In a second mode, the electric retarder suppliesonly a ratio of the requested braking torque. For example, 2/3 of thebraking torque may be supplied by the electric retarder and 1/3 may besupplied by the friction brake system. This configuration improveshandling by spreading the retarding torque according to the weight oneach axle.

Turning to FIG. 2, a logical block diagram illustrating a braking systemfor a machine including hydraulic friction brakes, an oil cooling systemand an electric retarder is provided. In some embodiments, a userinterface 116 allows the operator of the machine to view statusinformation relating to the braking system on a display 118. Displayedinformation may include whether the capacity of the electric retardingsystem to supply additional braking torque has been exceeded.Additionally, status information regarding whether a front brake enableselection is set, and automatic retarding settings and manual retardingsettings may be shown on the display 118. The front brake enableselection allows the operator to engage the front friction brakes. Thismay be done to assist machine braking in slick, wet or steep conditions.The selection can be made using the front brake retarding enable switch122, which will be more fully described below with reference to FIG. 3.

A manual retarder torque setting allows the operator to control thespeed of the machine by setting the manual retarder torque. For example,the manual retarder torque setting may be a lever the operator controlsto set a desired amount of retarding torque. The manual retarder torquecontrol sets a desired retarding torque for the electric retarder.Additionally, an automatic retarder torque may be automatically set bythe braking control system. For example, the machine may be programmedin advance, either by the operator or at the factory, to automaticallyprevent the ground speed of the machine from exceeding a threshold. Inone embodiment, the operator may set the automatic retarder torque valueat any time before or during machine operation. In this way, theoperator can adjust the automatic retarder torque value as conditionswarrant. If the automatic retarder torque and manual retarder torque areboth set, the system will multiply the values to determine a desiredmachine retarding torque. In another embodiment, the system uses thegreater of the automatic retarder torque and manual retard torquevalues. In some embodiments, the manual retarder cannot request moretorque than can be provided by the electric retarding system. In oneembedment, the desired machine retarding torque is the total desiredretarding torque from the axles of all wheels on the machine. Theautomatic retarder (also used for over-speed protection) sets thedesired machine retarding torque to control machine speed.

The user interface 116 includes a manual and automatic retarderinterface 120. The user interface 116 interacts with a controller 124.The controller 124 may include one or more control modules. In theillustrated embodiment, two electronic control modules (ECM) are used toimplement the controller 124. The drive-train ECM 126 controls elementsin the drive-train 128. The drive-train 128 includes the engine 100,generator 102, rectifier 104, inverters 106, motor 108, and chopper 112.When braking the machine, the electric retarding system 130 includes therectifier 104, inverters 106, motor 108, and chopper 112 and theresistor grid 114. In electric retarding mode, the drive-train ECM 126commands the electric retarding system 130 to provide a requesteddesired machine retarding torque and a ratio of retarding torque splitsbetween sets of wheels. Thus, the system drive-train ECM may command themachine to apply the proper ratio of torque splits between, for example,a set of front wheels and a set of rear wheels.

In one embodiment, the ratio of retarding torque splits is a ratio ofbraking torques between a front set of wheels and a rear set of wheels.This ratio may be based on the front brake retarding enable switch 122,the ratio will be more fully described with reference to FIG. 3 below.In some embodiments, the ratio of retarding torque splits between thefront set of wheels and rear set of wheels is based on the relativeweight acting on each set of wheels. For example, in a machine that isnot loaded, the ratio may be 50/50, but in a loaded machine the ratiomay be 1/3 braking torque to the front and 2/3 of the braking torque tothe rear.

In one embodiment, the drive-train ECM 126 receives signals indicatingthe front brake retarding enable switch 122 status, the manual retardertorque setting and the automatic retarder torque setting from a brakeECM 132. Based on these signals, the drive-train ECM 126 calculates thedesired machine retarding torque to be applied to the machine. Thedrive-train ECM 126 provides signals indicating the desired machineretarding torque and the requested electric retarding torque to thebrake ECM 132. The brake ECM, based on these signals, determines whetherthe requested electric retarding torque is sufficient to provide thefull desired machine retarding torque. If additional braking isnecessary to meet the desired machine retarding torque, the brake ECMrequests a ratio of additional braking torque from the front frictionbrake system 134 and the rear friction brake system 136. The frontfriction brake system 134 connects to a front set of wheels 138 and therear friction brake system 136 connects to a rear set of wheels 140. Inone embodiment the front friction brake system 134 and the rear frictionbrake system 136 are part of a hydraulic brake system 142. In thisembodiment, the hydraulic brake system includes a front brake solenoidvalve 144 for controlling the flow of hydraulic fluid to the frontfriction brake system 134. Likewise, a rear brake solenoid valve 146controls the pressure of hydraulic fluid to the rear friction brakesystem 136.

In large, heavy machines, such as large haul trucks used in off-roadapplications such as mining, friction brakes may overheat during use.Friction brakes continue to warm as they are applied. If the frictionbrake system overheats, component life may be reduced. Therefore, insome embodiments a brake cooling system supplies brake cooling oil tocool the front friction brake system 134 and the rear friction brakesystem 136. Brake cooling oil flows to both front and rear frictionbrakes. While front brake retarding is not enabled, oil flow is splitbetween front and rear brakes according to the brake requirements. Whilefront brake retarding is enabled, the majority of the cooling oil flowsto the front friction brakes. In one embodiment, the brake ECM 132provides a signal to a diverter solenoid valve, which connects to thebrake cooling flow system 148 (described in more detail with respect toFIG. 4). The brake ECM 132 and brake cooling flow system 148 can divertadditional flow to either the front friction brake system 134 or therear friction brake system 136. In one embodiment, the flow is based onthe ratio of retarding toque splits between set of wheels. In analternative embodiment, the brake cooling flow system 148 diverts theflow based on heat sensors in the front friction brake system 134 andthe rear friction brake system 136.

Turning now to FIG. 3, a flow chart illustrating one embodiment of abraking control process for a machine including hydraulic frictionbrakes and an electric retarder is shown. The illustrated embodimentshows the control process for a machine, such as an off-highway haultruck having a set of two front wheels disposed on opposite sides of thetruck and a set of four rear wheels, with two wheels disposed on eachside of the truck. At decision point 150 the system first determineswhether the front brake retarding enable switch 122 is enabled. If thefront brake retarding enable switch 122 is enabled, at step 152, thesystem commands the electric retarding system 130 to supply 2/3 of thedesired machine retarding torque. The system requests 2/3 of the desiredmachine retarding torque from the electric retarding system 130 because,in this embodiment, the electric retarding system is associated with therear wheels. More braking force can be applied to the rear wheelsbecause there are four rear wheels as opposed to the two at the front ofthe machine.

At step 154, the system limits the requested torque from the electricretarding system 130 to the maximum torque that can be provided by theelectric retarding system 130. At current operating conditions, theavailable electric retarding torque depends on the RPM of the motors.This can be accomplished in a number of ways including pre-calculatingthe maximum torque that can be provided by the electric retarding system130 or by receiving a feedback signal from the electric retarding system130 indicative of whether the electric retarding system 130 is providingthe requested retarding. In the illustrated embodiment, at step 156, thesystem requests the remaining 1/3 of the desired machine retardingtorque from the front friction brake system 134.

The rear friction brake system 136 is set to 2/3 of the desired machineretarding torque minus the requested torque from the electric retardingsystem 130 at step 158. Therefore, if the electric retarding system 130is providing all of the requested torque, then the rear friction brakesystem 136 is set to not provide any additional braking torque. Finally,at step 160, the front service brake solenoid current and the rearservice brake solenoid current are determined based on the front servicebrake pressure and rear service brake pressure needed to provide thecommanded front service brake torque and rear service brake torque.

If, at decision point 150, the front brake retarding enable switch 122is disabled, then the system moves to step 162. At step 162, the systemcommands the electric retarding system 130 to supply all of the desiredmachine retarding torque. At step 164, the system limits the requestedtorque from the electric retarding system 130 to the maximum torque thatcan be provided by the electric retarding system 130. As discussedabove, this can be accomplished in a number of ways includingpre-calculating the maximum torque that can be provided by the electricretarding system 130 or by receiving a feedback signal from the electricretarding system 130 indicative of whether the electric retarding system130 is providing the requested retarding.

In the illustrated embodiment, at step 166, the system requests 1/3 ofthe desired machine retarding torque minus 1/3 of the requested torquefrom the electric retarding system 130. Therefore, if the electricretarding system 130 is providing all of the requested torque, then thefront friction brake system 134 is set so as not to provide anyadditional braking torque. At step 168, the rear friction brake system136 is set to 2/3 of the desired machine retarding torque minus 2/3 ofthe requested torque from the electric retarding system 130. Therefore,the system maintains the braking ratio of 1/3 braking torque from thefront friction brake system 134 and 2/3 of the braking ratio from therear friction brake system 136 for any braking torque needed tosupplement the electric retarding system 130 braking torque. The systemnext enters step 160 as described above.

In one embodiment, the system monitors the temperature of the front andrear brakes using temperature sensors in the front friction brake system134 and the rear friction brake system 136. Based on the measuredtemperatures, the braking control process can request additional coolingflow from a brake oil diverter control process described in FIG. 5. Inanother embodiment, the system may predict the temperature and coolingflow needed.

Turning now to FIG. 4, a logical block diagram illustrating oneembodiment of a brake cooling system for a machine including frictionbrakes is shown. The illustrated embodiment shows four wheels, leftfront wheel 171, right front wheel 173, left rear wheel 175 and rightrear wheel 177. However, other embodiments may include additionalwheels. For example, in one embodiment a machine has two front wheelsand four rear wheels with two wheels deposed on each side of themachine. A brake cooling pump 179 connects to a cooling oil reservoir181 containing cooling oil. In an alternative embodiment multiple brakecooling pumps are utilized. In one embodiment the cooling oil is alsothe hydraulic fluid used throughout the machine in hydraulic systemssuch as hoists. In the illustrated embodiment, the brake cooling pump ispowered by an engine 183. The brake cooling pump 179 pumps cooling oilfrom the cooling oil reservoir through a filter 185 to a cooler 187. Thecooler may be a hydraulic cooler. After leaving the cooler 187, thecooling oil enters a diverter valve 189. The diverter valve 189 iscontrolled by a controller, such as the brake ECM 132 (FIG. 2). Thediverter valve can transmit cooling oil to the left front wheel 171,right front wheel 173, left rear wheel 175 and right rear wheel 177.

In one embodiment the diverter valve 189 sends 60% of the cooling oilflow to the rear wheels 140 and 40% of the cooling oil flow to the frontwheels 138 when both the front friction brake system 134 and the rearfriction brake system 136 are activated. When the front friction brakesystem 134 is activated, but the rear friction brake system 136 is notactivated, the diverter valve 189 sends 90% of the cooling oil flow tothe front friction brake system 134 and 10% to the rear friction brakesystem 136. Other embodiments of the invention send different amounts offlow to the front friction brake system 134 and the rear friction brakesystem 136 under various conditions. As shown in FIG. 2, in oneembodiment, the brake ECM controls the brake cooling flow system 148including the diverter valve 189. An exemplary scheme for controllingthe diverter valve 189 is described below with respect to FIG. 5.

In one embodiment, additional pumps, such as hoist pumps 190 provideadditional cooling oil flow. In this embodiment, the engine 183 powersboth the hoist pumps 190 and the brake cooling pump 179. The hoist pumps190 provide hydraulic fluid flow to hydraulic systems on the machine,such as to screens 192 and other hydraulic components 198 and hydraulicactuators 194. In this embodiment, the cooling oil is also hydraulicfluid and stored in reservoir 181. In alternative embodiments, thecooling oil is distinct from the hydraulic fluid. After leaving thehydraulic actuators 194, the fluid passes through a filter 196 and iscombined with the cooling oil flow from the brake cooling pump 179 in acombiner circuit (not illustrated). In the illustrated embodiment, thecombiner circuit is located before the cooler 187 and the diverter valve189. Therefore, the combined flow goes through the cooler 187 and thediverter valve 189 before flowing to the left front wheel 171, rightfront wheel 173, left rear wheel 175 and right rear wheel 177. Inalternative embodiments, the combiner circuit is located after thediverter valve 189 and provides additional flow to either the left frontwheel 171 and right front wheel 173 or left rear wheel 175 and rightrear wheel 177. In this embodiment, a second cooler may cool the floweither before or after the combiner circuit.

Turing now to FIG. 5, a flow chart illustrating one embodiment of abrake oil diverter control process for a machine is shown. At decisionpoint 170, the system determines its current state. The states include(1) divert to front and (2) divert normally. When the front frictionbrake system 134 is used, the system state is divert to front; when thefront friction brake system 134 is not used, the system state is divertnormally. In the divert normally state, the majority of brake coolingoil is diverted to the rear friction brake system 136 because the frontfriction brake system 134 is only used to supplement the electricretarding system 130 and therefore does not need additional cooling. Inone embodiment, in the divert normally state, sixty percent of the brakecooling flow is diverted to the rear friction brake system 136 and fortypercent of the flow is diverted to the front friction brake system 134.In the divert to front state, ten percent of the brake cooling flow isdiverted to the rear friction brake system 136 and ninety percent of theflow is diverted to the front friction brake system 134. In otherembodiments, the system senses the heat in the braking systems andautomatically adjusts flow as needed to cool the braking systems. Atstartup, the system can default to either state.

If, at decision point 170 the system is in the divert normally state,the system enters decision point 172. At decision point 172, the systemdetermines whether the front brake retarding enable switch 122 is on. Ifthe switch is not on, the system goes to block 174 and enters the divertnormal state. From block 174, the system returns to the initial decisionpoint 170. If the front brake retarding enable switch 122 is on, thesystem enters decision point 176. At decision point 176, the systemdetermines whether the rear friction brake system 136 is activated. Ifthe rear friction brake system 136 is activated, the system enters step174 and diverts the cooling flow normally. In one embodiment, atdecision point 176, the system determines whether the rear brakes havebeen used within some period of time, such as five seconds. If the rearfriction brake system 176 have not been applied, the system entersdecision point 178 and determines whether the front friction brakesystem 134 cooling oil reaches a threshold. If the oil does not reachthe threshold, the system enters step 174 and diverts the cooling oilnormally. If, at step 178 front friction brake system 134 cooling oil iswarm, the system enters step 180 and diverts additional cooling oil flowto the front friction brake system 134. The system then returns todecision point 170.

If, at decision point 170 the last state was not diverting normally, thesystem enters decision point 182. At decision point 182, the systemdetermines whether the rear friction brake system 136 is activated. Ifthe rear friction brake system 136 is activated, the system enters step174 and diverts the cooling flow normally. In one embodiment, atdecision point 182, the system determines whether the rear brakes hadbeen used within some period of time. If the rear friction brake system136 is not activated, the system enters decision point 184. At decisionpoint 184, the system determines whether the front brake retardingenable switch 122 is on. If the front brake retarding enable switch 122is on, the system goes to step 180 and diverts the cooling flow to thefront. If the front brake retarding enable switch 122 is off, the systemgoes to decision point 186. At decision point 186, the system determineswhether the front friction brake system 134 is activated. If the frontfriction brake system 134 is activated, the system enters step 180 anddiverts flow to the front friction brake system 134. If the frontfriction brake system 134 is not activated, the system enters step 174and diverts the cooling flow normally. In some embodiments, at decisionpoint 186, the system determines whether the front friction brake system134 has been applied within some period of time, such as 2 seconds.

INDUSTRIAL APPLICABILITY

The industrial applicably of the methods and systems for brakingmachines described herein will be readily appreciated from the foregoingdiscussion. The present disclosure is applicable to many machines andmany environments. One exemplary machine suited to the disclosure is alarge off-highway truck, such as a dump truck. Exemplary off-highwaytrucks are commonly used in mines, construction sites and quarries. Theoff-highway trucks may have payload capabilities of 100 tons or more andtravel at speeds of 40 miles per hour or more when fully loaded. Thetrucks operate in a variety of environments and must be able tonegotiate steep inclines in wet conditions.

These large off-highway trucks must be able to slow and stop even whentraveling down steep, wet slopes. Using the described methods andsystems, trucks can be slowed by using the electric retarding system 130or the electric retarding system 130 in combination with the frontfriction brake system 134, the rear friction brake system 136, or both.In some embodiments, the trucks are slowed using the electric retardingsystem 130 to save wear and tear on the front friction brake system 134and the rear friction brake system 136. However, in wet conditions, thetruck operator can manually engage the front friction brake system 134to aid machine handling. Additionally, the system can automatically usethe front friction brake system 134 and the rear friction brake system136 to aid in braking when electric retarding capacity is exceeded. Whenthe front friction brake system 134 and the rear friction brake system136 are in use, the system can automatically vary the cooling flow tothe systems using the brake cooling flow system 148.

Similarly, the methods and systems described above can be adapted to alarge variety of machines and tasks. For example, backhoe loaders,compactors, feller bunchers, forest machines, industrial loaders, skidsteer loaders, wheel loaders and many other machines can benefit fromthe methods and systems described.

It will be appreciated that the foregoing description provides examplesof the disclosed system and technique. However, it is contemplated thatother implementations of the disclosure may differ in detail from theforegoing examples. All references to the disclosure or examples thereofare intended to reference the particular example being discussed at thatpoint and are not intended to imply any limitation as to the scope ofthe disclosure more generally. All language of distinction anddisparagement with respect to certain features is intended to indicate alack of preference for those features, but not to exclude such from thescope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context.

Accordingly, this disclosure includes all modifications and equivalentsof the subject matter recited in the claims appended hereto as permittedby applicable law. Moreover, any combination of the above-describedelements in all possible variations thereof is encompassed by thedisclosure unless otherwise indicated herein or otherwise clearlycontradicted by context.

1. A method of cooling a first friction brake system and a secondfriction brake system in a machine having a brake cooling systemincluding fluid and a fluid diverter, the method comprising: determiningwhether the first friction brake system is activated; determiningwhether the second friction brake system is activated; circulating, witha first set of pumps including at least one pump, fluid through thebrake cooling system to the first friction brake system and the secondfriction brake system; circulating, with a second set of pumps includingat least one pump, fluid through at least one hydraulic system;combining the flow of fluid from the first set of pumps and the flow offluid from the second set of pumps; and diverting fluid between thefirst friction brake system and the second friction brake system basedon a first brake enable switch for the activation of the first frictionbrake system and based on a second brake enable switch for theactivation of the second friction brake system.
 2. (canceled)
 3. Themethod of claim 2 further comprising the step of delaying the diversionof the fluid until the fluid reaches a predetermined temperature. 4.(canceled)
 5. The method of claim 1 wherein the step of determiningwhether the first friction brake system is activated includes monitoringa manual retarder torque setting and an automatic retarder torquesetting.
 6. The method of claim 1 wherein the step of determiningwhether the second friction brake system is activated further includesmonitoring a manual retarder torque setting and an automatic retardertorque setting.
 7. The method of claim 1 further including the step ofdiverting 40% of the fluid to the first friction brake system when boththe first friction brake system and the second friction brake system areactivated.
 8. The method of claim 1 further including the step ofdiverting 90% of the fluid to the first friction brake system when thefirst friction brake system is activated and the second friction brakesystem is not activated.
 9. A friction brake cooling system comprising:at least one first pump in a first set of pumps connected to at leastone reservoir containing fluid and configured to provide a fluid flow toat least one valve in fluid communication with the first pump; at leastone second pump in a second set of pumps connected to the reservoir andconfigured to provide fluid to at least one hydraulic system andconfigured to provide fluid flow to the valve in fluid communicationwith the first pump and the second pump; a first friction brake systemin fluid communication with the valve and a second friction brake systemin fluid communication with the valve such that cooling fluid from thereservoir is pumped through the valve to the first friction brake systemand to the second friction brake system; at least one controllerconfigured to divert the cooling fluid flow through the valve to thefirst friction brake system and to the second friction brake systembased on a first brake enable switch for the activation of the firstfriction brake system and a first brake enable switch for the activationof the second friction brake system.
 10. The friction brake coolingsystem of claim 9 wherein the first pump is dedicated to the frictionbrake cooling system.
 11. The friction brake cooling system of claim 10wherein a flow of the fluid from at least one third pump is directed tothe valve.
 12. The friction brake cooling system of claim 9 wherein thefluid is hydraulic fluid used for at least one hydraulic systemassociated with the machine.
 13. The friction brake cooling system ofclaim 11 wherein the fluid is separate from hydraulic fluid used for atleast one hydraulic system associated with the machine.
 14. The frictionbrake cooling system of claim 9 wherein the valve diverts 90% of theflow to the first friction brake system when the second friction brakesystem is not activated and is configured to divert 40% of the flow tothe first friction brake system when the second friction brake system isactivated. 15-20. (canceled)